amend: stop specifying matcher, get all copies in wctx

When we're recreating the commit that we'll be committing, we don't want to
filter our copy information based on just the *new* [versions of the] files
we're amending. The test has an example of this case, but for clarity, the
situation is:

```
$ hg cp src dst && hg commit
<do some work>
$ hg amend some_unrelated_file.txt
$ hg status --copies
A dst
A some_unrelated_file.txt
```

What *should* happen is that `dst` should remain marked as a copy of `src`, but
this did not previously happen. `matcher` here only includes the files that were
specified on the commandline, so it only gets the copy information (if any, in
this example there's not) for `some_unrelated_file.txt`. When it goes to apply
the memctx to actually create the commit, the file copy information is
incomplete and loses the information for the files that shouldn't have been
affected at all by the amend.

Differential Revision: https://phab.mercurial-scm.org/D12625

mercurial/cmdutil.py

@@ -2915,9 +2915,9 b' def amend(ui, repo, old, extra, pats, op'
         # filectxs from the old commit.
         if changes or changeset_copies:
             # Recompute copies (avoid recording a -> b -> a)
-            copied = copies.pathcopies(base, wctx, matcher)
-            if old.p2:
-                copied.update(copies.pathcopies(old.p2(), wctx, matcher))
+            copied = copies.pathcopies(base, wctx)
+            if old.p2():
+                copied.update(copies.pathcopies(old.p2(), wctx))
 
             # Prune files which were reverted by the updates: if old
             # introduced file X and the file was renamed in the working

tests/test-amend.t

@@ -625,4 +625,4 b' cause them to be lost'
   $ hg status --change . --copies
   A new_file_amend_me
   A r0_copied
-    r0 (missing-correct-output !)
+    r0